Rapid decline of the CO2 buffering capacity in the North Sea and implications for the North Atlantic Ocean

Author Posting. © American Geophysical Union, 2007. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 21 (2007): GB4001, doi:10.1029/2006GB002825.New observations from the North Sea, a NW European shelf sea, show that between 2001 and 2005 the CO2 partial pressure (pCO2) in surface waters rose by 22 μatm, thus faster than atmospheric pCO2, which in the same period rose approximately 11 μatm. The surprisingly rapid decline in air-sea partial pressure difference (ΔpCO2) is primarily a response to an elevated water column inventory of dissolved inorganic carbon (DIC), which, in turn, reflects mostly anthropogenic CO2 input rather than natural interannual variability. The resulting decline in the buffering capacity of the inorganic carbonate system (increasing Revelle factor) sets up a theoretically predicted feedback loop whereby the invasion of anthropogenic CO2 reduces the ocean's ability to uptake additional CO2. Model simulations for the North Atlantic Ocean and thermodynamic principles reveal that this feedback should be stronger, at present, in colder midlatitude and subpolar waters because of the lower present-day buffer capacity and elevated DIC levels driven either by northward advected surface water and/or excess local air-sea CO2 uptake. This buffer capacity feedback mechanism helps to explain at least part of the observed trend of decreasing air-sea ΔpCO2 over time as reported in several other recent North Atlantic studies.S. Doney and I. Lima were supported by NSF/ONR NOPP (N000140210370) and NASA (NNG05GG30G)

Export of Pacific carbon through the Arctic Archipelago to the North Atlantic

During an east-to-west transect through the Canadian Arctic Archipelago, dissolved inorganic carbon (DIC) and total alkalinity (TA) were measured. The watermass composition throughout the Archipelago is determined using TA and the seawater oxygen isotope fractionation (δ18O) data, and the carbon characteristics of these waters are examined. The influence of the Mackenzie River is primarily limited to the upper water column in the western Archipelago while the fraction of sea-ice melt water in the surface waters increases eastward with maximum values at the outflows of Jones and Lancaster Sounds. The depth of Pacific-origin upper halocline waters increases eastward through the Archipelago. In the western Archipelago, non-conservative variations in deep water DIC are used to compute a subsurface carbon surplus, which appears to be fueled by organic matter produced in the surface layer and by benthic respiration. The eastward transport of carbon from the Pacific, via the Arctic Archipelago, to the North Atlantic is estimated, and the impact of increased export of sea-ice melt water to the North Atlantic is discussed. Research highlights: ► Inorganic carbon data from east–west transect in Arctic Archipelago. ► Water mass composition determined with TA, S and d18O. ► Fraction of sea-ice melt water increases eastward though Archipelago. ► Non-conservative variations in DIC indicate subsurface carbon surplus. ► Eastward transport of carbon from Pacific to Atlantic estimated

Changes in the North Atlantic Oscillation influence CO2 uptake in the North Atlantic over the past two decades

International audienceObservational studies report a surprisingly rapid decline of the CO2 uptake in the temperate North Atlantic Ocean during the last decade. We analyze these changes using numerical model simulations for the period 1979-2004, with interannually varying atmospheric forcing. The reorganization in ocean circulation is a major driver of these CO2 system changes. North Atlantic Oscillation (NAO) climate patterns are overlain by transient events such as the Great Salinity Anomaly. Our analysis indicates that the recent rapid shifts in CO2 flux are decadal perturbations superimposed on the secular trends and highlights the need for long-term ocean carbon observations and modeling to fully resolve interannual variability, which can obscure detection of the long-term changes associated with anthropogenic CO2 uptake and climate change

The Marine Biodiversity Observation Network Plankton Workshops: Plankton Ecosystem Function, Biodiversity, and Forecasting—Research Requirements and Applications

ISSN:1539-6088ISSN:1539-607

Changes in the North Atlantic Oscillation influence CO2 uptake in the North Atlantic over the past 2 decades

Observational studies report a rapid decline of ocean CO2 uptake in the temperate North Atlantic during the last decade. We analyze these findings using ocean physicalbiological numerical simulations forced with interannually varying atmospheric conditions for the period 1979-2004. In the simulations, surface ocean water mass properties and CO2 system variables exhibit substantial multiannual variability on subbasin scales in response to wind-driven reorganization in ocean circulation and surface warming/cooling. The simulated temporal evolution of the ocean CO2 system is broadly consistent with reported observational trends and is influenced substantially by the phase of the North Atlantic Oscillation (NAO). Many of the observational estimates cover a period after 1995 of mostly negative or weakly positive NAO conditions, which are characterized in the simulations by reduced North Atlantic Current transport of subtropical waters into the eastern basin and by a decline in CO2 uptake. We suggest therefore that air-sea CO2 uptake may rebound in the eastern temperate North Atlantic during future periods of more positive NAO, similar to the patterns found in our model for the sustained positive NAO period in the early 1990s. Thus, our analysis indicates that the recent rapid shifts in CO2 flux reflect decadal perturbations superimposed on more gradual secular trends. The simulations highlight the need for long-term ocean carbon observations and modeling to fully resolve multiannual variability, which can obscure detection of the long-term changes associated with anthropogenic CO2 uptake and climate change

The Marine Biodiversity Observation Network Plankton Workshops:Plankton Ecosystem Function, Biodiversity, and Forecasting—Research Requirements and Applications

Plankton is a massive and phylogenetically diverse group of thousands of prokaryotes, protists (unicellular eukaryotic organisms), and metazoans (multicellular eukaryotic organisms; Fig. 1). Plankton functional diversity is at the core of various ecological processes, including productivity, carbon cycling and sequestration, nutrient cycling (Falkowski 2012), interspecies interactions, and food web dynamics and structure (D'Alelio et al. 2016). Through these functions, plankton play a critical role in the health of the coastal and open ocean and provide essential ecosystem services. Yet, at present, our understanding of plankton dynamics is insufficient to project how climate change and other human-driven impacts affect the functional diversity of plankton. That limits our ability to predict how critical ecosystem services will change in the future and develop strategies to adapt to these changes